The compressors are 125 HP screw type and the oil is air cooled   they run 24/7  .
And they really crank out a lot of heat 140of to 160of air temp .

We had to install a 500 gal tank and a boost pump to raise the hot  water pressure we had on the fourth floor of the building. Were we set it up it was only 20 feet from the compressors.
And ties in to a 1500 gal steam heated water heater.

We placed a air to water heat exchanger over the hot air being exhausted by the compressor.

The water form the pumps bypass was plumed to the heat exchanger and back to the tank.
We are only raising the water temp to about 90o F but this gave us one heck of a savings.
It was only an after thought as we all ready planing to put in boost pump and tank in any way.
 The best part for me was getting payed for something I like playing with : )  

Now the Briggs tube and shell will be a test to see how much and how fast can I heat water
with engin exhaust. Its one of many irons I have in the fire right now.

Right now I have been working on a tower design of my own.
So much fun so little time : )